The placebo effect is one of the clearest demonstrations of how thinking affects the body. Believing that someone has given you an effective cure for a problem (although they have only given you a sugar pill or waved something over your head) can not only cause emotional calming, but actually change the physical experience within the body. For example, a study of prostate disorder symptoms reported a two-year improvement among the men who were given a placebo and informed that it would help.

In a more common example of how thinking influences the body, have you had this experience? You went to bed late one night during the work week, looked at the clock, calculated the hours until you had to get up, and thought to yourself , I'm going to be exhausted tomorrow." In the morning, you felt miserable as you climbed out of bed and dragged yourself to work. All day long you reinforced this feeling by repeating "Am I tired!" Sound familiar? Now replay the same scene, but this time it happens when you are on vacation. You stay out late into the night, dancing, partying. Going to bed, you anticipate the exciting prospects of the next day - new adventures, new sights, new people. You remember that some people thrive on only a few hours of sleep a night and, armed with this thought, you retire happily. The next day you leap out of bed ready for the magic, barely giving a moment's reflection to the amount of sleep you've had. Your thoughts have energized your body.

There are other examples. Years ago, when we were sharing dinner at John's house in Mill Valley, California, we heard a rumbling noise. John, who had been through three earthquakes in eleven months, immediately labeled the rumbling "earthquake." The thought of an earthquake was enough to get our hearts beating faster, blood flowing with greater intensity, hormones activated, stomachs churning. There was no earthquake, but it took a lot longer to convince our shaky hands and queasy stomachs than it did to reassure our minds. Our bodies responded as actively to the imagined danger as they would have to a real one.

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